Increased resolution of chromosome behavior will be attempted through cytogenetic characterization of meiosis in males of drosophila ananassae with particular emphasis on control of crossing over by genes regulating the occurrence and distribution of exchanges. A secondary goal will be elucidation of high mutation frequency associated with a nonsegregating mutator element. BIBLIOGRAPHIC REFERENCES: Hinton, C. W., and J. E. Downs, 1975. The Mitotic, polytene and meiotic chromosomes of Drosophila ananassae. J. Heredity 66: 353-361.